Method and apparatus for treating pulverized material



G. H. FRASER. METHOD AND APPARATUS FOR TREATING PULVERIZED MATERIAL.

I918- Patented July APPLICATION FILED SEPT.25 I912. RENEWED AUG.1,385,67.

.1 In I I I w S m I WITNESSES:

UNITED STATES PATENT OFFICE.-

GEORGE HOLT FRASER, OF BROOKLYN, NEW YORK.

METHOD AND APPARATUS FOR TREATING PULVERIZED MATERIAL.

1,385,674. Application filed September 25, 1912,

To all whom it may concern:

Be it known that I, Gnoner. HOLT FRAsER, a citizen of the United States,residing in the borough of Brooklyn, county of Kings, city and btate ofNew York, United States of America, have invented certain new an usefulImprovements in Methods and Apparatus for Treating which the followingis a specification.

This invention relates to means for treating finely divided material, ormixtures of various pulverized substances, and to grinding, screeningand mixing the same, and aims to provide improved methods for suchtreatment, and improved means especially applicable to carrying out theimproved methods provided.

Heretofore it has been common to pul verize mixed materials of differentphysical characteristics or difierent specific gravity, to grade thematerial according to size so that material too large for pulverizlngshould be separated from that to be fed to the pulverizer, and thatsufficiently pulverized should be separated for subsequent treatment.Ordinarily a coarse screen or grizzly is used to remove the coarsestmaterial, and a fine screen or air separator is used to extract thepowder, the intermediatematerial being returned to the pulverizer forfurther screening. The coarse screen is used to prevent the coarsermaterial from wearing the finer separator, and its product ma be mixedwith the reject of the latter for return to the pulverizer after thefine sep arator has operated on the material.

The coarse material or mixture is supplied from a bin or suitablesource, and the fine material is removed as made to a bin or suitabledischarge. The various successive operations are effected by suitableapparatus arranged in the desired order and connected by any usual meansfor delivering from one to another.

In such operations difficulties have arisen from the liability of themixture to change in proportions at different times, especially when oneingredient is lighter than another or of different physicalcharacteristics. This changing of the relative percentages of thedifferent materials in the mixture affects the chemical qualities of themass, and. where subsequent chemical treatment is required it is verydisadvantageous.

In pulverizing, difficulty sometimes results from the liability ofmaterial of intermedi Specification of Letters Patent.

Pulverized Material, of

Patented July 26-, 1921.

Serial No. 722,233. Renewed August 15, 1918. Serial No. 250,079.

ate fineness occurring in irregular quantitles, and variations 1n theproportions of coarse material and intermediate material injuriouslyaffect the operation of the apparatus, as well as causing variations inthe proportions of the mixture.

This invention aims to provide a method whereby material can bepulverized Without materially altering the character of the mixture,whereby pulverization' can be effected with great uniformity, andwhereby the operation of pulverizing material may be automaticallyregulated by the material being treated. I

t also aims to provide improved apparatus for pulverizing, separatingand treating finely divided material or mixtures.

To this end in carrying out the preferred form of the improved process,the pulverized material is withdrawn from treatment as finished inquantitiescorresponding with the quantities of fresh material introducedfor terial, and the intermediate material present regulates the entranceof fresh material. The effect of this is that the quantity of materialbeing treated is maintained so uniformly that substantially the sameconditions prevail throughout treatment, and its treatment must becompleted before additional material can enter, thus precludingimportant changes in the percentages of the-materials constituting themixture, since the charge under treatment must be disposed of beforeadditional material can be treated,

while the materialas finished is continuously withdrawn and iscontinuously replaced by the automatic control of the fresh supply. I

Where the is effected by a fluid current or air separator and thematerials differ greatly in specific gravity, this precautionagainstchanging of the mixture is especially important, as in separationof finished material pulverizer,

such instances the air separation would tend to remove the lightermaterial from the heavier regardless of fineness, in case a continuingsupply of material were available before all of the material present hadbeen pulverized.

This invention also provides improved means for carrying out theimproved process, which means preferably comprise a pulverizer, a coarsescreen, a fine separator, a supply bin, an elevator, and meansconnecting these parts in succession to effect the desired results.

In the accompanying drawings Figure 1 shows the preferred utilization ofthe im-' proved process, and. the preferred embodiment of the improvedapparatus, and is a vertical axial section of a. pulverizing, screening,separating, feeding and discharging system especially applicable forcarrying out these lmprovements, the view being cut approximately on theline 1-1 of F i s. 2 and 3 and looking in the direction of t e arrows;Fig. 2 is a fragmentary vertical section thereof cut at right angles toFig. 1 approximately on the line2-2 of Fig. 3 and looking in thedirection of the arrows, and Fig. 3 is a fragmentary horizontal sectionthereof cut approximately on the line 33 of Fig. 2 and looking in thedirection of the arrows.

ReferringBto the drawing, A indicates a v a drive pulley therefor, G thegrinding chamber thereof, l) the outlet coilduitthereof, E the inletconduit thereof, F a coarse screen, (Jr its tailings spout, H an airseparator, I its tailings s out, J its fine chamber, K its fine spout,the fine discharge, M the coarse rock supply or feed bin, N the feedhopper, O the feedregulating or controlling chamber, P the elevator orother means communicating between the parts 0 and E, and Q the supplyregulator.

The parts of the device shown may be of any suitable or usualconstruction and connected in any desired order or manner, but it ispreferred to use a pulverizer of the ring and roll type in which thematerial is centrifugally carried by the ring and free to dischargetherefrom regardless of the fineness of the material, and to drive thepulverizer from a suitable source of power, and to drive the other partsfrom the pulverizer, connecting the parts in succession so that theoperation of all will be coincident.

As shown, the coarse screen or grizzly immediately succeeds thepulverizer, and is disposed below the latter to receive the dischargetherefrom, having a revolving distributing disk R on which thisdischarge falls and by which it is thrown centrifugally to the outerupper edge of the screen, which is a vlbratorynon-rotative member.

It is preferable to construct the screen in the shape of an invertedcone elastically suspended from above by. a spring S, so that it maydescend under load or shock and will rise when released, and its upwardmovement will be suddenly arrested to give it a vibration or upwardbumpto jar material out of its meshes. A'lever or arm T hinged to thecasing a above the screen and in the path of a projection on the disk Rserves to depress the screen when struck by the, disk, thus vibratingthe screen.

Preferably the screen is provided with swinging or spring strikers Ushown'as both extending toward the shaft ,of the disk R and movable intothe path of swinging hammers W thereon, so that they will be struckthereby when the screen is depressed to agitate it for cleaning.

The screen F is preferably extended within and discharges its fines ontothe inner face of a revolving distributer X, which is preferably aninverted cone mounted on and revolving with the shaft V, and having anoutlet surroundingand spaced apart from the outlet of the screen F. Thedistributer X revolves with sufficient speed to raise and distributeover its upper edgethe material fine enough to pass the screen F, whichmaterial is thrown against a deflector Y, from which it falls onto thereceiving cone Z of the air separator, crossing Lthe outlet thereof, sothat the outflowing air current can blow the powdered material ofdesired fineness out of the falling material and into the settlingchamber J of the air separator, the air from which returns within theapron .7), over the tailings cone 0, through the outlet 01 of thereceiving cone, to the blades 6 of the blower 7, which latter is aconical wall surrounding the cone distributer X and revolving therewith,and having radial blades between its inner face and the adjacent face ofthe distributer. The receiving cone Z is yieldingly supported by springs9 so that it can be depressed until it are brought into the path ofrevolving strikers i to jar it.

The t'ailings cone 0 communicates with the cylindrical upper end of thespout I, which end surrounds and is concentric of the coarse spout G,which latter receives the coarse material from the coarse screen F. Thedistributer X has bottom outlets j for. any material failing to rise inthat this material may drop through the bottom of the distributer andinto the receiving coneZ and flow through the bottom out-' let 03thereof to the spout I. All material too large to be floated slides downthe receiving cone Z and escapes through its outlet to the spout I.

The spout G discharges above and preferably vertically down through thematerial being discharged from the spout I, which latter dischargeslaterally into the regulatg'ch m er 0. If. i d sired to use the itsinner projections the distributer, so

"material flowing through the spout I, in-

stead of to further grind it, the door is in the bottom of this spout isturned up so as to let the material in the spout I escape through thechute Z, but if this material is to be reground, this door is closed asshown'and the material enters the regulating chamber with the coarsematerial from the spout G.

The regulating chamber 0 discharges its material through a bottom outletm to the boot of the elevator P, which raises the material to the feedinlet E, so that there is an past a gate n and endless circuitcommunicating through the pulverizer, the screen, elevator back to thepulverizer, through which the coarse reject from the screen and theintermediate reject from the separator may be continuallyre-fed to thepulverizer, so that this material will be. reground.

The fine material settling in the dust chamber J flows into its spout Kand escapes therefrom to the fine bin L.

The fresh feed from the chamber M flows a rock crusher or crushing roll0 to the feed chamber N, from W'hlCll it passes through outlets p to theregulating chamber 0. These outlets preferably have adjustable lips 9within the chamber 0 which extend inwardly, so that the angle from thetop of the outlet 79 to the edge of the lip or shelf 9 is adjustable tocontrol flow of the material escaping from the feed bin. The feed binsurrounds one or more sides of the regulating bin and has severaloutlets thereto, preferably one on each of two sides, for example asshown in the drawmgs wherein the chamber or bin 0 is shown as avertically extending pipe or tubulanmember having an imperforate Wallopposlte each outlet p from the fresh feed hopper N, the openings ;0entering the bin 0 laterally intermediate of its bottom outlet m and itsupper super osed fine and coarse tailings inlets I and Theregulating binis similar to a vertical conduit or chute, and its inlet forintermedlate and coarse material is above the inlets for fresh material,and its outlet is below these inlets. The intermediate material fallsinto the regulating chamber, and if it is not removed through the outlettherefrom by the elevator as rapidly as it enters, it fills up thischamber until it rises above the outlets p of the feed bin, whereuponthe intermediate material in front of these outlets arrests flow offresh material from the feed bin, WlllCll it does by closing the outletstherefrom. The removal of the intermediate material below these outletspermits this fiow to automatically occur until it has sufii-i cientlyfilled the regulating chamber to again prevent inflow thereto. Theremoval of material by the elevator through the outlet from theregulating chamber progresses uniformly, and so long as there s anymaterial the separator, and thebin, and vice versa.

mum necessary to control fresh feed will continue to be carried throughthe circuitof the system until it is pulverized before additional freshmaterial can enter.

In this manner it is assured that the charge of material being treatedwill be finished before more material can enter, and the excessiveremoval of a lighter ingredient from the mixture by the air separatorwill be precluded, since the heavier ingredients left in the system willprevent infeed of fresh material until the air separator has removed a'sufficient quantity to permit the infeed of fresh material toautomatically resume.

Should the escape of uninterrupted, the entrance of fresh material .canbe automatically controlled by the arrangement described, but it ispreferred to further insure that the fresh material supplied to thesystem shall accord with the removal of finished material therefrom.This preferably is accomplished by utilizing the weight of fine materialremoved to control the supply of fresh material to the feed I As shown,the'finished material spout K discharges into a Weighing bucket 1through agate which is controlled by a weighing device t, and thisfinished material be bucket and gate are connected by a lever u with agate w and a bucket w for the feed bin, which are controlled by aweighing device y. The bucket 03 is shown assupported from its weighingdevice by the tri catch .2, so that the gate to is open and fresmaterial for the feed bin is entering the bucket w. "When the desiredquantity has entered the bucket its weight tilts the beam until the tripcatch releases, whereupon the bucket rapidly falls, lowering the gate wto prevent further infeed of fresh material, tilting the lever u toraise the bucket 1' and open the gate 8 until its trip catch 2 engagesand supports this bucket, the bucket m dumping and the bucket 1'closing. all according to any well known method of automatic weighing,of which the parts illustrated are intended to be diagrammaticrepresentations. bucket x will discharge its weight load of fresh feedinto the feed bin N and the bucket 1' will collect an equal load offinished material from the spout K, after. which the operation will bereversed, the bucket 1- dumping its load into the fine bin L and closingthe fine outlet and restoring the bucket m and opening the feed outlet.

As shown, the elevator is driven from the pulverizer by a belt a, andthe distributer attained to for the coarse screen and blower for the airseparator, as Well as the feeder for the fresh rock, are driven by abelt b therefrom, so that all movable parts of the system coincide withthe pulverizer in operation, thus insuring stoppage of all in case ofstoppage of the pulverizer, which prevents undue accumulation in anypart of the system.

In this manner an automatic mechanical uniformity prevent variations inoperating conditions and minimize resulting changes.

Ia operating according to my improved process, one or several grades ofthe treated material, or of the material in process of treatment, willbe utilized to control the feed of other grades of material or of freshmaterial, according to the requirements of the particular process orconditions of use. The coarser material being projected through theintermediate material, will ma-v terially reduce the tendency of thematerial to segregate according to size within the regulating chamber.The control of flow of the fresh or coarse material by the intermediatematerial will insure precedence to e the latter in treatment, andgreatly diminish kept from clogging,

i tion,

tendency to variations in the percentage of ingredients in the mixtureif a mixed material is being treated.

In using my improved apparatus the circular or conical vibrator movablyand yieldingly mounted in the screen'wlllbe easily and being nested orpositioned within the conical redistributing disk, will occupycomparatively little space, and the distributing disk being likewisenested within the receiving cone of the air separator, and the blower ofthe latter bemg disposed in conical arrangement between the distributingcone and the receiving cone, will further minimize the space requiredfor these several parts. The revolving striker in conjunction with theyielding and movably mounted receiving cone, will aid in keeping thecone clean, thus reducing the steepness necessary therefor.

It will be seen that this invention provides improvements in processesof treating materials which can be variously arid advantageously availedof in whole or in 'part, and it will be understood that the invention isnot limited to the particular details of arrangement, application or useset forthas constituting its preferred adaptation, since it can beemployed in whole or in part according to such modifications and inconnection with such devices as circumstances or the-judgment of thoseskilled in the art may dictate, without departing from the spirit of theinvention; and it will also be understood that the improvements inapparatus this invention provides are not lim-- ited to the particulardetails of construcarrangement and combination set forth of supply andremoval may be.

as constituting the preferred form thereof,, since these improvementsmay be used in whole or in part according to such modifications ascircumstances or the judgment of those skilled in the art may dictate,without departing from the spirit of the invention. v v

For example in practising the improved process it is not essential thatthe screen be either beneath or directly following the pulverizer, asany suitable means for communicating between the parts in any desiredsuccessive stage .may be employed.

While these improvements in apparatus include in their preferred formscreens and separators located next following the pulverizer, andcircular or conical devices nested within one another for compactness,and having annular communicating ducts and contracting annular outlets,it will be understood that it is not essential that these be used inpractising parts of the invention, since the elements may beindividualized and connected in any suitable arrangement, or anysuitable grizzlies or separators may be employed, if desired.

VVlule. the regulating ho per or bin is shown as disposed below al theparts and as feeding from its bottom to the mill through the medium ofthe elevator, and the plurality of hoppers or bins for different gradesof material to be fed are shown as beneath the mill, and the feed bin assur-' rounding the regulating bin, instead of these parts being abovethe mill and the regulatmg bin discharging directly into the latter, itwill be understood that the arrangement shown is not essential, beingpreferred for compactness and convenience of access, and that theplurality of bins may be located as desired, and the connectionscorrespondingly arranged to dispose them in any manner so that fee-d tothe pulverizer may be controlled by any of the .several grades ofmaterial which it is desired shall govern the operation, the bins andtheirinlets and out- I lets being constructed and connected in propermanner to enable the grade of material whichis to have precedence tointerrupt or control the inflow of the other grade or grades.

What I claim is 1. The improved process of reducing material whichconsists in subjecting it to a crushing treatment, removing the materialof the desired fineness as formed, separating the coarser material,again subjecting the separated material to crushing treatment, andutilizingthe weight of such separated material to control entrance offresh mate- '125 rial to the mass.

2. The improved process of reducing material which consists insubjecting it to crushutilizing the weight of the removed material tocontrol entrance of fresh material to the mass.

3. In apparatus for grinding materials, a pulverizer, a separator,passages for fines, intermediate and coarse materials in communicationwith said parts, means operated by the weight of the fine materialremoved from said separator, means measuring the fresh material suppliedto said pulverizer, and means controlled by said weight operated meansand controlling the supply of freshmaterial to said separator.

' 4. In combination, means affording an endless path for material, meansfor returning coarse material to said path by gravity comprising adownwardly extending gravity chute or passage having an upper inlet anda confined downwardly extending chamber for such material and having alower outlet, and having a lateral inlet in the side of said chamber forfresh material intermediate of said upper inlet and said lower outlet,and means for feeding by gravity fresh material to said path throughsaid lateral inlet to 'said chamber laterally of the direction of flowof said coarse material therein.

5. In combination, means affording an endless path for material, meansfor feeding fresh material to said path, and means for returning coarsematerial to said path comprising a passage or chute having an upperinlet and a lower outlet in vertical alinement and having intermediatethereof a down wardly extending'chamber between and in verticalalinement with said inlet and said outlet having a lateral inlet betweensaid upper inlet and said lower outlet, and a gravity chutecommunicating with said fresh feeding means and discharging through saidlateral inlet into said chamber.

6. In combination, means affording an endless path for material, meansfor feeding fresh material to said path, and means for returning coarsematerial to said path comprising a tubular member or spout having alower outlet and having an upper inlet for said coarse material spacedabove said outlet, and having intermediate of said'lower outlet an upperinlet, a lateral gravity inlet communicating with said fresh feedingmeans, and having a wall opposite said lateral inlet forsustainingmaterial descending through said member from said upper inlet againstinflowof freshfeed through said lateral inlet.

7. In combination, means for feeding different grades of materialcomprising a downwardly extending chamber or chute having an upper inletfor material of one grade, a lower outlet, and intermediate thereof aconfined chamber and a lateral inlet for another grade of material, anda second chute or member at theside of and communicating with thelateral inlet of said downwardly extendin chute for feeding anothergrade of material laterally into the latter.

'8. In'combination, means for feeding material comprising a chamber orchute having a downwardly extending tubular portion having an upperinlet, a lower outlet, and having a downwardly extending chamber betweensaid inlet and said outlet, and hava lateral inlet to said chamber belowsaid upper inlet and above said lower outlet, a gravity chutecommunicating with said lateral'inlet, and means for adjusting saidlateral inlet to regulate flow through the latter.

9. In combination, means for producing pulverized material affording anendless circuit or path for material to be pulverized andcomprisingmeans having a vertically extending crushing chamber affording acomplementary portion of such path constituting a downward way for suchmaterial and having a lower outlet, an air separator below andsuccessive to said chamber and having a downwardly extending chamberaffording a successive complementary portion of such path and a downwardway for such material, and having means surrounding such way for freeingsuch material of fines, an elevator affording a complementary part ofsaid path and having a lower inlet below and communicating with theoutlet of such air separator for such material for receiving andelevating such material, and having. an upper outlet above andcommunicating with such crushing chamber for delivering such materialthereto, .and means for operating said parts in correlation, and meansfor supplying material to be pulverized to such circuit.

,10. In combination, means for producing pulverized material affordingan endless circuit or path for material to be pulverized and comprisingmeans having a vertically extending, crushing chamber affording acomplementary portion of such path censtr tuting a downward way for suchmaterial and having a loweroutlet, an air separator below and successiveto said chamber and having a downwardly extending chamber affording asuccessive complementary portion of such path and a downward way forsuch material, and having means surrounding such way-for freeing suchmaterial of fines, an elevator affording a complementary part of saidpath and having a lower inlet below and communicating with the outlet ofsuch air separator for such material for re ceiving and elevating suchmaterial, and having an upper outlet above and communicating with suchcrushing chamber for delivering such material thereto, means foroperating said parts in correlat1on, and

. complementary portion of such path constituting tutin a downward wayfor such material and Iiaving a lower outlet, a separator below andsuccessive to said chamber and havin a downwardly extending chamberaffordlng a successive complementary portion of such path and a downwardway for' such material, and having means surrounding. such way .forfreeing such material of fines, an elevator affording a complementarypart of said path and having a lower inlet below and communicating withthe outlet of such air separator for such material for receiving andelevating such material, and having an upper outlet above andcommunicating with such crushing chamber for delivering such materialthereto, means for operating said parts in correlation, and means forsupplying material to be pulverized to such circuit as fines areseparated from said separator.

12. In combination, means for producing pulverized material affording anendless circuit or path for material to be pulverized and comprisingmeans having a vertically extending crushing chamber affording acomplementary portion of such path constia ,downward way for suchmaterial and having a lower outlet, a separator below and successive tosaid chamber and having a downwardly extending chamber affording asuccessive complementary portion of such path and a downward way forsuch material,

and having means surrounding such way for freeing such material offines, an elevator affordlng a complementary part of said path andhaving a lower inlet below and communicating with the outlet of suchseparator for such material for receiving and elevating such material,and having an upper outlet above and communicating with such crushlngchamber for delivering such material thereto, means for operating saidparts in correlation, and means for supplying material to be pulverizedto said circuit in like quantity of fines separated from said circuit.13. In combination, means for producin pulverized material comprisinmeans a fording an endless path afl'or 'ng an inlet for material to bepulverized and an outlet for pulverized material and comprising meanshaving a chamber affording a complementary portion of said ath andconstitutmg a way for material in said path, means for causingmaterialuto .circulate through said ath, means for withdrawing finematerial fgom said path, means for progressing the residue of partiallypulverized.

for material in said path, means for causing material to circulatethrough said path, means for withdrawing fine material from said path,means for progressing a residue of coarse material in said path pastsaid inlet, means for supplying through said inlet additionalpulverulent material, and

means for causing such residue material in said ath to control inflowthrough said inlet of such additional material. f

15. In combination, meansafl'ording an endless path for pulverulentmaterial afmaterial fording an inlet and an outlet and comprismgconveying means having a chamber at fording a complementary portion ofsaid a path and constituting a way for such material in said path, meansfor causing material to circulate through such path, means forwithdrawing from said path a portion of such material circulatingthrough said path, means for progressing in said path the residue ofsuch material therein past said inlet, means for supplying through saidinlet additional means for causing such residue material in said path tocontrol inflow through said inlet of such additional material.

16. Incombination, means affording an endless path for pulverulentmaterial affording an inlet and an outlet and comprlsing elevating meanshaving a vertically extending chamber affording a complementary path andconstituting a way portion of said for such materlal in said path, meansfor causing material to circulate through said path, means forwithdrawing through said material to said path, and

outlet a portion of such material from said path, means for progressingthe residue of such materialinsaid path ast said inlet, means forsupplying throug said inlet additional materialto said path, and meansfor causing such residue material in said through said inlet mg chamberafl'ording a complementary portlo-n of said path and constituting a wayfor material in said path, means for causing material to circulatethrough saidpath, means for separating fine material from suchmaterial-in said path, means affording an outlet for fine material fromsaid path, means in said path between said crushing chamber and elevatoraffording an inlet to said path for additional material, means forprogressing such residue of material in said path ast,,said inlet, meansfor supplying throng said inlet additional material to said path, andmeans for causingsuch residue material in said path to control inflowthrough said inlet of, such additional materiaL' a 18. In combination,means .for separating fine material comprising means afiording anendless path for pulverulent material to be separated and comprisingaseparator having a separating chamber affording a complementary portionof said path and constituting a way for such material in said path,

velevating means for elevating material 1n said path comprising avertically extending chamber affording a complementary portion of saidpath and constituting a way for such material in said p'ath, means forcausing such material to circulate through said path, means afl'ordingan outlet for fine material from said path communicating with said pathbetween said separatorand said elevator for'withdrawing from said pathfine material separated from the material in said path, means afi'ordingan inlet to said path between said elevator and said separator, meansfor progressing the residue of such material in said path past saidinlet, means for supplying to said path through said inlet additionalpulverulent material, and means for causing such residue material .insaid path to control inflow through said inlet of such additionalmaterial.

19. In combination, means affording an endless path affording an inletfor pulverulent material and an outlet for fine material and comprisingelevating means having a chamber affording a complementary portion ofsaid path and constituting a vertically extending way for such materialin said path, separating means for separating material from the materialin said path having a downwardly extending chamber affording acomplementary portion of said path and constituting a gravity way fordownward flow of materialnin said path, means for progressing theresidue of matefrom such material in mi ,pulverulent material to rial insaid path by gravity past said inlet for controlling inflow through saidinlet, and means for introducing additional material into said path bygravity through said inlet. I

20. In combination, means aflording an endless path for pulverulentmaterial and comprising elevating means for elevating such materialhaving a vertically extending chamber affording a complementary portionof-said path and constituting an upward way for such material in saidpath, separating means for separating coarse material path having achamber affording a complementary portlon of said path and constitutinga gravity way for material said elevating means and said separatingmeans affording a conduit for coarse material afl'ording a complementaryportion of said path, means for withdrawin from said path the residue ofsuch materlal in said path through said outlet, means for progressingsuchcoarse material in said path ast said inlet, means for introducinginto said path through said inlet additional material, and means forcausing such coarse material in said path to control inflow through saidinlet of such additional material. 21. In combination, a separator forseparating fine material from ulverulent material having an inlet andaving an outlet for fine material and an outlet-for coarser material, anelevator communicating between said latter outlet and said inlet forraising coarser material discharged through said latter outlet andreturning it to said inlet, and means for feeding additional pulverulentmaterial to be separated to said separator controlled by the materialdischarged through said outlet f or coarser material. L

22. In'combination, a separator for separating fine material frompulverulent material having an inlet and having an outlet fordischarging fine material and an outlet for coarser material, and means.for feeding be separated to said separator controlled by the finematerial discharged through said outlet for fine material.

In witness whereof, I have hereunto signed my name in the presence oftwo subscribing wltnesses.

, GEORGE HOLT FRASER. 1 Witnesses: 4 v

FRED WHITE THOMAS F. WALLACE.

in said path, means between

